The streptozotocin-diabetic rhesus monkey is being studied as a model of human juvenile (insulin-deficient) diabetes. Ocular, renal, metabolic, and physiologic parameters are followed, and show progressive although early lesions of diabetic microangiopathy, as compared to normal findings in age-matched control monkeys. Total pancreatectomy is performed in a second group of monkeys, and the pancreas is subjected to a variety of methods of islet isolation and purification. Optimal yields, least contamination with acinar tissue and enzymes, and most efficient route of inoculation are under study. Islet cell hormone production by the transplanted tissue as well as in the STZ-diabetic and pancreatectomized monkeys, is documented with insulin assay, C-peptide analysis, and glucagon production. The autotransplanted tissue is found to secrete insulin and glucagon and to respond to appropriate physiologic studies. Pancreatic tissue from neonatal and fetal primates and from adult monkeys sacrificed by other investigators, is utilized for culture and cyropreservation experiments. Long-term culture and fetal-maternal reimplantation experiments are under way.